Blend file hash keeps changing
I was interested in this so did a little research.

A blender save works by directly copying the scene data from memory to disk. This makes the save fast since there is no need for a 'conversion' stage.

This means that any change to how that data is in memory will result in the same change when in a blend file. This could be trivial changes like the order of variables in a list.

read this for more details: http://archive.blender.org/development/architecture/blender-file-format/

"Blend-files can be different when stored on different hardware platforms or Blender releases. There is no effort taken to make blend-files binary the same."

Basically it means that hashing the file cannot be used to check for content changes.

R